//https://leetcode.cn/problems/distinct-subsequences/


class Solution {
public:
    int numDistinct(string s, string t) {

        int m = t.size(), n = s.size();
        vector<vector<double>> dp(m + 1, vector<double>(n + 1));
        for(int j = 0; j <= n; j++) dp[0][j] = 1; // 初始化
        for(int i = 1; i <= m; i++)
            for(int j = 1; j <= n; j++)
            {
                dp[i][j] += dp[i][j - 1];
                if(t[i - 1] == s[j - 1]) dp[i][j] += dp[i - 1][j - 1];
            }
        return dp[m][n];
    }
};